| 摘要 |
PURPOSE:To obtain a polyester film low in content of large protrusions, excellent in slidability and suitable for magnetic tapes, etc., containing fine particles of excellent dispersibility comprising amorphous alumina silicate of a specified composition synthesized by a wet process. CONSTITUTION:Fine particles having an average particle diameter of 0.005-5mum, being amorphous according to X-ray diffractometry and having a composition of the formula (wherein X and Y are each an equivalent ratio to SiO2, X is 0.01-0.2 and Y is 0.001-0.3) are synthesized by, for example, a process comprising reacting an aqueous water glass solution with an aqueous aluminum sulfate solution and forming a precipitate. These amorphous alumina silicate fine particles are added to the system of synthesis of a polyester resin (e.g., polyethylene terephthalate resin) to produce a polyester containing 0.001-3wt% fine alumina silicate particles. This resin is formed into the purpose polyester film. |
